1. Field of the Invention
The present invention relates to a light scanning device which writes an electrostatic image on an image bearing member, and more particularly to a light scanning device which writes an electrostatic image on an image bearing member by scanning an image bearing member with a light beam deflected by a light deflector.
2. Discussion of the Background
Image writing sections of image forming apparatuses such as digital copiers, printers and facsimile machines include an optical image writing unit (i.e., a light scanning device) which scans an image bearing member such as photoreceptors with a light beam, which is modulated according to image signals and which is deflected by a light deflector and passes through an optical device, to form an electrostatic image on the image bearing member. The thus formed electrostatic image is developed with a developer including a toner to form a toner image on the image bearing member.
Recently, a need exists for an image forming apparatus, which can produce high quality images, and therefore, a need exists for a light scanning device, which can write an optical image with high resolution. Light scanning devices typically emit a laser light beam through a transparent covering member covering a light irradiation opening (e.g., dust-proof glass plates), which is provided to prevent dust from entering the light scanning devices. When toner particles and dust (such as paper dust) are adhered to the transparent material, a problem in that transmission of a laser beam is worsened and thereby qualities of an electrostatic image formed on the image bearing member are deteriorated occurs.
On the other hand, a need exists for a small-sized image forming apparatus. Therefore, arrangement of a light scanning device in image forming apparatuses becomes diversified. For example, there is a case where a light scanning device is arranged so as to be on the same level in position as that of an image bearing member or to be located below an image bearing member. In this case, a problem in that toner particles used for developing an electrostatic image on the image bearing member are adhered to the transparent covering member easily occurs.
In attempting to solve the problem, published unexamined Japanese patent application No. 2002-267983 (hereinafter referred to as JP-A) discloses a technique in that a dust-protective cover is provided on the transparent dust-proof glass plate such that dust is not adhered to the dust proof glass plate. If dust is adhered to the glass plates, the dust-proof glass is cleaned after detaching the cover therefrom, and a technique in that a cleaning mechanism for cleaning the dust-proof glass is provided to remove dust adhered to the dust-proof glass with a cleaning pad thereof.
JP-As 2002-127495 and 09-80875 have disclosed a technique in that the transparent covering member (made of a glass plate) has a constitution so as to be detached from the light scanning device, and a technique in that a slidable flame having a cleaning member is provided to clean the dust-proof glass.
Further, JP-As 2004-17607 and 07-128959 have disclosed a technique in that a bar cleaner having a pad thereon is provided or a technique in that a bar cleaner is provided on the case of a magazine of the image forming apparatus, and the surface of the transparent covering member is cleaned by the cleaner when the magazine is detached to be replaced.
However, recently in order to produce high quality images, a toner having a small average particle diameter is typically used and therefore the problem in that the transparent covering member of the light scanning device is contaminated with the toner is caused more frequently than ever. Particularly, spherical toner has poor cleaning property, i.e., spherical toner particles easily pass through a cleaning blade, resulting in increase of the amount of residual toner particles on an image bearing member. Therefore, the chance of contamination of a transparent covering member with residual toner particles is increased.
In addition, recently there is a tendency such that users perform maintenance of their image forming apparatus as much as they can. Therefore, the above-mentioned problem is easily caused.
Because of these reasons, a need exists for a light scanning device which can maintain good laser light emitting property over a long period of time by means of user's simple cleaning operation.